US2884584A

US2884584A - Mechanical current converters

Info

Publication number: US2884584A
Application number: US362534A
Authority: US
Inventors: Brueckner Paul
Original assignee: AUGUST HAMILTON SCHILLING
Current assignee: AUGUST HAMILTON SCHILLING
Priority date: 1952-06-30
Filing date: 1953-06-18
Publication date: 1959-04-28
Anticipated expiration: 1976-04-28

Description

April 2 8, 1959 P. BRUECKNER 2,384,584

MECHANICAL CURRENT CONVERTERS Filed June 18, 1953 l? I? a a 6 L 8 -L 8 h 2 x3? ,9 --:[1 a 1 '8 :T: I 5 g g" :5 g 2 5 3 Inventor? ATTORNEY United States Patent 0 MECHANICAL CURRENT CONVERTERS Paul Brueckner, Misburg, near Hannover, Germany, assignor to August Hamilton Schilling, Atherton, Calif.

15 This invention relates to mechanical current converters having associated therewith commutating reactors and auxiliary current converters connected in parallel with the disconnecting path.

The present invention has for its object to realize during the commutation process as much as possible a sparkless opening of the mechanically actuated contacts located in the disconnecting paths of the current converters.

Another object of the invention is to decrease to a great extent the dimensions and the cost of commutating reactors which have been proposed already for accomplishment of this task and which have become known in connection with shunt current paths in parallel with the contacts of the mechanical current converters.

It is a further object of the present invention to reduce the voltage effective in the commutation circuit and determining the dimensions of and therewith the cost of such commutating reactors.

In order to accomplish this task it has already been 35 proposed to connect quenching rectifiers in parallel with the commutating reactor and to the mechanically actuated contact. In this case said quenching rectifiers have been designed as dry-plate rectifiers, thyratrons and other common current converters. Such installations, however, have only a very small overload capacity, thus requiring correspondingly high constructional expenditure. Although a certain part of the costs resulting therefrom can be saved through the decreased expenses for the commutating reactors, the final result does not bring forth the 1; deciding technical and economical advantage whose realization, is the object of the present invention. This object. of the invention comprises the task of reducing the voltage effective in the commutating circuit down to few hundredths of the voltages which hitherto prevailed. 5') Therewith it becomes possible to accomplish the further objective of the present invention that is, to design the commutating reactor as a simple core encompassing the current conveying conductor, thus eliminating completely any auxiliary winding.

All these problems, including mechanical current converters having commutating reactors and auxiliary current converters connected in parallel to the disconnecting path Where an auxiliary voltage source is provided in a path parallel to the mechanically operated contacts, are solved according to the invention by providing on the one hand, controllable current converters having with regard to current very high overload capacity, preferably current converters whose current conducting arc in each phase is initiated by an ignition process and is quenched through the valve effect of the current converter, and on the other hand these problems are solved by providing commutating reactors located only in the branch circuit of the mechanical current converter and arranged for a 0 potential corresponding to the difference between the auxiliary voltage and the sparking voltage of the auxiliary current converter.

Consequently, in contrast to known arrangements where the commutating reactors carry the entire main current and the shunt paths are assigned to convey the smaller current during no-load intervals caused by the common type of large commutating reactors, according to the invention the main current is cornmutated by means of an auxiliary voltage on the auxiliary current converter toward the end of the current passage time. Thus the mechanical contact has only to break a circuit in which the small differential voltage of auxiliary voltage and sparking voltage is effective. Therefore, a commutating reactor of the hitherto common size is unnecessary. In order to facilitate the task of the mechanical contact, a very small commutating reactor, having a size of only few percent of that of hitherto common commutating reactors, is connected in series to it. The cost of such a small commutating reactor is no longer of importance. In most cases it will be sufiicient to design the commutating reactor as a simple iron core encompassing the current conveying conductor, thus making it possible that eventually auxiliary windings can be completely dispensed with.

The drawing shows by way of example a circuit according to the present invention. In said drawing,

Fig. 1 illustrates a circuit diagram of a three-phase oneway rectifier constructed in accordance with the present invention; while Fig. 2 shows the circuit of a periodically actuated ignition circuit for an ignitron serving as an auxiliary rectifier.

Mechanical contacts 2 are connected in known manner to the three phases of the current converter-transformer 1. The circuit closes over the load 3 and an eventually arranged smoothing reactor 4. Highly overloadable and controllable current converters, for example, ignitrons 5 and auxiliary voltage sources 6 are shunted across the mechanical contacts 2. Besides this, commutating reactors 7, of extraordinarily reduced size when compared with commutating reactors of known design are provided in the current branch of the mechanical contacts. Additionally to each switch contact 2 of the main circuit, there is provided in each case a rotatably arranged switch bridge 2 having the contact parts 8 and actuated by means of the driving device for the main contacts 2. The contact parts 8 bridge momentarily and periodically the auxiliary contacts 9 which are in the ignition circuit of an ignitron 5 whose circuit is illustrated by way of example in Fig. 2.

Fig. 2 shows the transformer 11 which charges a condenser 10 by way of a valve 12 so long as the contact bridges 2' do not connect the auxiliary contacts 9. If, however, the contacts 9 are bridge, then the condenser discharges over the ignition point of the ignitron and there effects the introduction of an arc.

The manner of operation of the circuit is as follows:

The mechanical contact 2 associated with a phase is closed during the longest period of the current passage time through said phase and the shunted auxiliary current converter is opened thus allowing the current to flow over the mechanical contact 2 only. The auxiliary current converter 5 is ignited at a desired moment towards the end of the current passage time. Toward the end of a current passage period the auxiliary current con verter 5 is ignited by momentary actuation of the auxiliary contact bridge 2 which occurs at a predetermined advance with respect to the moment of opening of the main contacts 2, as the auxiliary contacts 9 are momentarily connected through the auxiliary contact bridges 2. The discharge current circuit for the fully charged condenser 10 is thereupon closed and the ignition of the arc in the associated ignitron is initiated. The auxiliary voltage source in this case must be proportioned in such manner that it covers the sparking voltage of the auxiliary current converter 5 and is capable of commuting the main current from the mechanical contact to the shunted auxiliary current converter Within an appropriate interval of time which may range approximately from 5 to electrical degrees. After the main current has been taken over by the auxiliary current converter 5, a low voltage, caused by the difference between auxiliary voltage (voltage source 6) and sparking voltage of the auxiliary current converter 5, applies to the series connection of the main contact 2 and the commutating reactor 7. The commutating reactor 7 now makes possible the practically sparkless opening of the contact 2.

As has been already mentioned above, the commutating reactor 7 only needs to be dimensioned for the indicated very small differential voltage.

In the embodiment illustrated, ignitrons are shown as auxiliary current converters. However, other arrange ments or types as, for example, are type current converters may be used as auxiliary current converters. A determining fact is their high overload capacity with regard to current, as otherwise uneconomically large arrangements would become necessary.

It is not necessary, as shown in the drawing, to design the auxiliary voltage sources 6 as independent transformers. On the contrary, it is suflicient, if, for instance, the main transformer is provided with additional terminals for tapping the auxiliary voltage.

There is the further particular advantage with the arrangement proposed according to the invention that, as already has been mentioned, the moment of ignition of the auxiliary current converters can be chosen absolutely according to desire. If the moment of ignition of the auxiliary current converter is kept constant with time in relation to the opening moments of the mechanically actuated contacts, the contacting duration of the mechanical contacts 2 can remain constant without regard to modulation and load condition of the mechanical current converters, thus saving a considerable amount of expense for regulator installations.

For the ignition of the additional current converter there are available still other electrical circuits diifering from that shown in Fig. 2 and in themselves known, which circuits can operate in accordance with the type and construction of the auxiliary current converter also without additional contacts. The arrangement illustrated in the drawing of ignitrons in combination with additional auxiliary contacts represents a circuit which can be realized at small expense.

I claim:

1.. Mechanical current converter comprising in combination: mechanically actuated circuit breaking contacts provided in the current conveying phase lines of the current converter, current paths arranged in parallel with the current breaking contacts, controllable auxiliary current converters arranged in said parallel paths, said auxiliary current converters being effective in the same direction as the current converter itself and being connected to be periodically traversed by operating current prior to and during the commutation, said auxiliary current c0nverters being constructed as current converters having high current overload capacity, means for producing an auxiliary voltage in the parallel paths, said auxiliary voltage being only slightly greater than the sparking voltage of an auxiliary current converter, and commutation reactors arranged only in the current branch of the mechanical current converter, said commutation reactors being di-- mensioned for a voltage equal to the difference between the auxiliary voltage and the sparking voltage of an auxiliary current converter.

2. Mechanical current converter according to claim 1,

including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter.

3. Mechanical current converter according to claim 2, wherein said commutation reactors consist exclusively of an iron core encompassing the current conveying conductor.

4. Mechanical current converter according to claim 1, including means for igniting the auxiliary current converter at the end of the passage time of the operating current.

5. Mechanical current converter according to claim 1, including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, said auxiliary current converters being constructed as ignitrons.

6. Mechanical current converter according to claim 1, including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, said auxiliary current converters being constructed as arc current converters.

7. Mechanical current converter according to claim 1,

' including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, and control means adapted to keep the moments of ignition of said auxiliary current converters at a constant time interval from the moment of opening of the mechanical contacts.

8. Mechanical current converter according to claim 1, including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, and means for keeping constant the duration of mechanical contacting independently of the modulation of the current converter.

9. Mechanical current converter according to claim 1, including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, and means for keeping constant the ignition of the auxiliary current converter in relation to the moment of opening of the mechanical contacts, said constancy being adapted to keep constant the opening of the contacts of the mechanical current converter independently of the load current.

10. Mechanical current converter according to claim 1, including means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, and auxiliary contacts on said current converter adapted to ignite the auxiliary current converters.

11. Mechanical current converter comprising in combination mechanically actuated circuit breaking contacts provided in the current conveying phase lines of the current converter, current paths arranged in parallel with the current breaking contacts, controllable auxiliary current converters arranged in said parallel paths, said auxiliary current converters being effective in the same direction as the current converter itself and constructed as current converters having high current overload capacity, means for producing an auxiliary voltage in the parallel paths, and commutation reactors arranged only in the current branch of the mechanical current converter, said commutation reactors being dimensioned for a voltage equal to the diiference between the auxiliary voltage and the sparking voltage of an auxiliary current converter, and means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, said means for producing an auxiliary voltage consisting of independent transformers.

5 12. Mechanical current converter comprising in combination: mechanically actuated circuit breaking contacts provided in the current conveying phase lines of the current converter, current paths arranged in parallel with the current breaking contacts, controllable auxiliary cur- 5 the sparking voltage of an auxiliary current converter, 15

means for initiating current-conducting arcs in each phase by an ignition process and for extinguishing the arcs by valve actions of the current converter, and a current converter transformer, said means for producing an auxiliary voltage in the parallel paths consisting of auxiliary terminals on the current converter transformer.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,610,231 Wettstein Sept. 9, 1952 2,619,617 Pakala Nov. 25, 1952 FOREIGN PATENTS 221,725 Switzerland Sept. 1, 1942 911,544 France July 10, 1946